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Nerve tissue
Microscopic structure – practice 2012
Nerve tissue - morphology
cells : 1.neurons and 2.glial cells
• extracellular material is extremely reduced replaced by
glial branched process
• neurons receive stimuli and conduct nerve impulse via
their processes
• action potential transmission to the next cell through
synapses (= intercellular contacts)
• extensive vasculature with variable amount of connective
tissue both in CNS and PNS
• blood-brain barrier in CNS
Tissue microscopic structure: cells with
processes – integrated communicating network
neuron theory – contact junctions among neurons
Neurons and neuroglia are cells with processes
Neuron, neuroglia, blood vessel
N3 – cerebellum,HE
• NEURON is structural and functional unit of
nerve tissue
Nerve tissue microstructure (example 2 –
brain )
Glial c.
Neuron
Perikaryon (soma, cell body)
receptor region, integration, trophic centre
• nucleus
• large, lightly basophilic, with dispersed chromatin, prominent
nucleolus
• RER
• abundant → substance of Nissl - tigroid
• Golgi apparatus
• only in perikaryon!
• cytoskeleton (neurofilaments)
• mitochondria
• inclusions
• lipofuscin, melanin
Cytoskeleton
• Microtubules
– axonal transport (anterograde, retrograde, microtubuleassociated motor proteins used ATP – dynein, kinesin)
– shape regulation
• Neurofilaments (intermediate filaments in neurons)
– resistance against deformations
– regulatory process
• Microfilaments (aktin)
Dendrites
receptor region
principal recieving site
• arborisation (branching) increases receptive area of the cell
(100 000 contacts and more)
• dendritic spines (site of synapse - postsynaptic membrane,
actin microfilaments
• neurofilaments (NF-L, NF-M, NF-H), other cytoskeleton units,
proteosynthetic apparatus except GA
• always non- myelinated
Axon
conductive region
• transmit stimuli in the form of action potential to other
neuron or effector cell
• 1 neuron has 1 axon
• metabolically dependent on perikaryon
• Golgi type I neurons – motor neurons of CNS with long
axon (up to 1 meter) terminate on skeletal muscle
• Golgi type II neurons – short axons
• axon hillock, initial segment – site of action potential
generation
• axonal transport transport vesicles, mitochondria ,
proteins…by anterograde x growth factor, viruses..by
retrograde
Synapse
effector region, unidirectional transmission of nerve impulse
presynaptic (axonal) terminal + postsynaptic (dendritic,
somatic, axonal) membrane
site of chemical message transmission in response to action
potential
presynaptic : synaptic vesicles with neurotransmitters,
microtubules+kinesin, mitochondria
synaptic cleft
postsynaptic membrane of effector cell:
1. nerve cell
2. muscle cell
3. secretory cell
Neuroglia
“connective tissue“ of CNS
• provide neurons with structural support and maintain local
condition for neuronal function
• forming 50% volume of CNS
• 10 x more abundant than neurons
• histological staining
• impregnation by Ag, Au salts, histochemical technics
Glia - types
–
–
–
–
astrocytes
oligodendrocytes
microglia
ependymal cells
B44 Brain/ Cerebrum (HE)
B45 Brain/Cerebrum
LFB, luxol fast blue, myelin staining
B46 Small brain, cerebellum HE
N3 - cerebellum HE
• Purkyňova buňka
• Granulární neuron
Spinal cord / cross section - B48
B48 Spinal cord HE
Ependym
• epitheloid arrangement of
ependymal cells
• neural tube neuropithelium
remnant
B49 Autonomic ganglion
B50 Peripheral nerve
Peripheral nerve
Astrocytes
(protoplasmic, fibrous)
•
•
the largest of neuroglia
astrocytic end feet- connection to vessels
and neurons providing movement of wastes
and metabolites to and from neuron
• regulate ionic concentration in intercellular
space
• contribute to blood-brain barrier
(together with tight junctions of endothelal
cells)
mechanical support of neurons
proliferation - glial scar
glial fibrillary acidic protein
Oligodendrocytes
• smaller, ↓intermediate fibres,
darker nucleus
• formation of myelin sheath
• myelinisation of several axons
Microglia
• the smallest, dark elongated
nucleus
• they migrate to the sites of
dead cells, proliferate,
phagocytes (dead cells, cell
debris…)
• mesoderm -derived
Ependym
• epiteloid arrengement
uspořádání
– remnant of
neuroepithelium of
neural tube
* secretory elements
(cerebrospinal fluid)
component of choroid plexus of
brain ventricles and central
canal of spinal cord
Nerve fibres
• axons provided by special connective tissue capsules of
ectodermal origin
• axons:
– unmyelinated
– myelinated
Unmyelinated nerve fibres
Myelinated nerve fibres
• in PNS: axons are invaginated
into cytoplasm of enveloping
Schwann cell (sheath is formed
by layers of modified cell
membranes) x in CNS: cell
process of oligondrocytes form
sheath
• nodes of Ranvier and
internode, 1-2 mm
• Schmidt-Lanterman´s
incisures
Myelinated nerve fibres
Eg 13 - Myelinizovaný axon
N8 – Ganglion HE
Satelite cells
Neuron
Arrangement of nerve tissue in the body, CNS
and PNS
• CNS
• clusters of neurons – cell body:
layers, columns (grey matter)
• bundles of axons: tracts,
fasciculi, lemnisci (white
matter)
• (grey and white matter
differentiation: according to
the content of myelin)
• PNS
• clusters of neurons: ganglia
• bundles of axons:
cranial
spinal
peripheral nerves